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Re: Repairing Cracked Masonry

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Alas Scott you have exposed my weakness...I am not much of a keyboarder...that is the reason for my brevity. ;-( I suspect you are a good typist and I envy you for that. I'll try to sum up the whole situation;

-8 story brick faced w/ cmu backup steel framed building on 9' deep spread footings in stiff clay (high PI) -Cavity space is filled w/ grout but cmu has water proofing membrane on it. What ties it has are corrugated metal type -Cmu is unreinforced and unconnected to structure but is grouted to floor beam above so I suspect the beam is bearing down on the wall enough to hold it in place.
-no MWFRS
-Several inches of foundation movement
-and on and on and on.

One big expensive mess up. We can underpin the foundation at the corners only because the building flares out at the bottom 2 floors except at the corners. But because for the nature of the building geometry. and actual movement this underpinning should thwart the movement from the foundation.

But then there is the unreinf cmu that can only tolerate 6psf lateral loading and it needs to withstand 37 psf. and of course it needs to attached to the structure to transfer the lat load and to perform as a shear wall etc.

Then there needs to be braced frames on the first to floors because the cmu wall stops at the 3rd floor. Then of course the brick system has so many flaws it needs to be taken off and rebuilt properly...so basically we need to rebuild the building from the inside out. Big Big bucks that the owner doesn't have!!!

Since the fdn is the biggest contributor to the crack (which is causing a very leaky building) Well start there and fix the other problems later acknowledging that movement will still occur just not as much. But the cracks have to be sealed now (that is after all the main complaint). So I want to give them an option that will minimize he possibility of the caulk joint failing at least right away. By all rights the building should be put out of it's misery but that's not possible so we'll give it something to "manage the pain."

And yes yes there is more....but do you know how long it took me to type that ;-) !!!

Rand







----- Original Message ----- From: "Scott Maxwell" <smaxwell(--nospam--at)engin.umich.edu>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, November 09, 2004 5:51 PM
Subject: Re: Repairing Cracked Masonry


Rand:

You have piqued my curiosity.  Are the 1" cracks vertical (this seems to
have been assumed by some but your original post was not clear)?  If so,
how high do they go?  Is the 1" crack width uniform through the depth of
the brick masonry?  How often are the cracks occuring?  Do you have an
idea of when they open up vs. when they close (i.e. seasonal, daily, etc)?

Basically, I am wondering what is causing them.  As at least one other
person had suggested (James Cohen), it would be prudent to figure out what
is causing the movement before attempting a repair on the cracks.  In your
response to James, you seem to already be aware of this and have an idea
what is causing the movement in the cracks.  Now, however, I am
curious...are you willing to share what you think is causing the cracks to
move?

I think that James' point is still well worth noting...if you know what is
causing the movement and "cure" that, then fixing the crack should be much
easier.  If the movement issues are solved, then the previously attempted
fix of caulking the crack should work (might still require a backer rod).
IF the movement issues cannot be "cured" then it is likely that there will
be no repair option that will work well.

Regards,

Scott
Adrian, MI


On Tue, 9 Nov 2004, Rand Holtham, P.E. wrote:

Stan,

It looks like that's what they've used previously. These are large cracks
say 1" wide. The rebar will not fully restrain movement, it is after all
just a 1/4" rod but hopefully would add ductility to the joint and hopefully restrian the movent that disloges the caulk. Yes there is a lot of hope in
that sentence. Point well taken though.

Harold,

I have my doubts too, that's why I posted... what do you mean develop a
mortar doesn't an epoxy mortar already exist?

David,

The Engineer who evaluated the problem 15 yrs ago had the same conclusion as you did. But he neglected to notice the 4 to 5" of differential movement in the foundation and that there is no discrete lateral force resisting system. Differential foundation movement alone can cause a variety of crack shapes
vert, horiz, stairstep then add the displacement from wind loading.

Now set me straight on the expanding brick...As the brick expands it creates
a 1" gap??? I thought you leave a 1" gap so the material can expand into
that gap without causing distress....(I'm with you that clay expands and
concrete shrinks over time but...)


Keep it coming this is productive, Thanks guys :>

Rand



----- Original Message -----
From: "David Fisher" <dfisher(--nospam--at)fpse.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, November 09, 2004 12:15 PM
Subject: RE: Repairing Cracked Masonry


> Sounds like "Mother Nature" has created a control joint where none
> previously existed...
>
> Is that true?
>
> What, if anything, did the architect specify?
>
>
>
> Since it's vertical and not stepped, it would appear to be the result > of
> thermal/moisture stresses and not structural issues...
>
>
> As we know, clay expands when wet while Portland cement products (CMU)
> Shrink over time.
>
>
> If it's a naturally occurring control joint, its probably needed in
> exactly
> or
> Nearly that spot.
>
>
> Treat it as such: fill the gap with a compressible filler and backer
> rod/seal the
> Exterior side of the joint.
>
>
>
> David L. Fisher SE PE
> Fisher + partners
> 372 West Ontario
> Chicago 60610
>
> 312.573.1701
> 312.573.1726 fax
>
> 312.622.0409 mobile
>
> www.fpse.com
>
> -----Original Message-----
> From: Rand Holtham, P.E. [mailto:rand(--nospam--at)sigmaengineers.com]
> Sent: Tuesday, November 09, 2004 11:49 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Repairing Cracked Masonry
>
> Lister,
>
> For the sake of brevity I will condense a very complex problem into a
> simple
>
> question that I have no answer for:
> I have a large crack (actually many large cracks) in the brick veneer > on
> an
> eight story building. This crack allows water to penetrate the building
> and
> attempts to caulk have been unsuccessful as the crack moves thereby
> dislodging the caulk. I am contemplating the addition of a small (say > #2)
> rebar in the grout joint  (grind out joint repoint with epoxy mortar or
> other?) so that the reinforcing crosses the crack in essence stitching > the
> crack together. Then applying the caulk with the idea that the added
> reinforcing will control the crack from movement beyond that which the
> caulk
>
> can tolerate. I can see extending the reinforcing 24" or 36" on each > side
> of
>
> the crack This is not to stop the building movement but to facilitate
> waterproofing the brick facing.
>
> My simple question is--- will the rebar bond well enough to the brick > and > mortar for this to be effective? Any thoughts will be greatly > appreciated
> ~:-).
>
>
> Rand
>
>
>
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